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Friday, September 9, 2011

Windows 8 Feature 'fast startup mode'

Are you the sort of person who prefers to shut your PC down at the end of the day rather than hibernate it or put it to sleep, but do you still want to the system to start up fast? Windows 8 has a new feature that will be of great interest to you.

The feature is called ‘fast startup mode’ and it is a hybrid between a standard cold boot and restoring your PC from a hibernated state. How doe sit work? Gabe Aul, director of program management in Windows, explains over on the Building Windows 8 blog:

The key thing to remember though is that in a traditional shutdown, we close all of the user sessions, and in the kernel session we close services and devices to prepare for a complete shutdown.

Now here’s the key difference for Windows 8: as in Windows 7, we close the user sessions, but instead of closing the kernel session, we hibernate it. Compared to a full hibernate, which includes a lot of memory pages in use by apps, session 0 hibernation data is much smaller, which takes substantially less time to write to disk. If you’re not familiar with hibernation, we’re effectively saving the system state and memory contents to a file on disk (hiberfil.sys) and then reading that back in on resume and restoring contents back to memory. Using this technique with boot gives us a significant advantage for boot times, since reading the hiberfile in and reinitializing drivers is much faster on most systems (30-70% faster on most systems we’ve tested).

How much faster is this than a standard cold boot? Take a look at this:

Here’s how fast startup is different to a traditional cold boot:

And here it is in action:

The notebook used in that video is an EliteBook 8640p (Intel Core i7-2620M, 8GB, 160GB SSD).

This is impressive stuff, but I’m left with some questions:

This is not a cold boot, so will there be a degradation in performance over time when using it? It seems that using the Restart command will revert to a cold boot.

How do applications and antivirus and all the other junk people have on their systems affect fast startup? In many cases it isn’t Windows that slows down boot times, but all the other junk installed.